As precision and smaller tolerances become the expected norm in computational and processing machines, better equipment used to fabricate components is expected by manufacturers. To house and protect magnetic disks, wafer disks, or similar inventory during a manufacturing process, special carriers or containers, also known as boats, baskets, or cassettes are used. One kind of conventional container comprises a disk cassette having an open top and an open bottom, a top cover, and a bottom cover. Each is formed separately by injection molding. The disk cassette is integrally formed of a rigid plastic, such as polycarbonate, that may be conductive. It has elongate side walls that extend vertically on the upper portions and curve inwardly on the bottom portions to the open bottom, and vertical end walls with U-shaped contours defining a U-shaped opening. The top cover may be formed of polycarbonate, polypropylene, or many similar injection grade polymers. It is shaped to follow the contour of and continuously align with the top of the side walls and end walls, and typically snaps onto a catch at or rests on the lower end of the U-shaped contours in the end walls. The bottom cover may be formed of a similar polymer as the top cover and is generally rectangular and tray shaped. It is molded to engage and be frictionally retained by the open bottom of the disk cassette. Examples of this kind of container are found in U.S. Pat. No. 4,557,382 and U.S. Pat. No. 5,253,755. Another example is Narisawa et al., U.S. Pat. No. 6,070,730, Disk Container, which is hereby incorporated herein by reference.
Several other variations of this kind of container are disclosed in Kikuchi, U.S. Pat. No. 4,721,207, Hard Disk Container; Boehm et al., U.S. Pat. No. 4,779,732, Container for Plurality of Disk-Shaped Articles and Container Part Thereof; and Maenke, U.S. Pat. No. 5,253,755, Cushioned Cover for Disk Container. Each of these containers conforms to one or two common themes. First, the bottom covers are designed to engage and be frictionally retained by a bottom edge or perimeter of a disk cassette. Second, the top covers have flaps that come over the side walls of the disk cassette and attach to the side walls just below the U-shaped contours. In Boehm, one flap extends off the top cover and the other off the bottom cover. These flaps conceal an ingress such as the U-shaped contours or an orifice providing access to the disks through the end walls.
The means for attaching the flaps is often similar to the following: “The closure parts 3 and 4 have an approximately L-shaped cross-section . . . They are advantageously produced from an elastically deformable plastics material, in particular a thermoplastics material, so that the arm of the L-form or the wall 9 or 9′ can be bent through a total distance sufficient for it to project beyond the projection 8 or 8′. Because of their springiness, the walls 9 and 9′ snap over the projections 8 and 8′ and lock the parts 1 and 2 together.” (Quoting from U.S. Pat. No. 4,779,732.) This attachment means is a source or cause for increased particulation on the end disks housed in a disk carrier, which is undesirable in a clean room manufacturing process. As a consequence, manufactures often put “dummy” disks, disks that are not intended for use in a product, on each end of the disk carrier to shield the other disks. If these dummy disks were not needed, through put could be increased at a substantial cost savings to the manufacturer.
In addition to the above described problem, disk carriers do not have a complete path to ground for dissipating static or other electrical charge away from disks and thereby further protecting the disks against accidental arching and other unintended events. Often, only the disk cassette is conductive.
Therefore, it would be advantageous to have a disk carrier that could significantly reduce the particulation created by opening and closing a disk carrier and could efficiently and cost effectively dissipate undesirable electrical charge away from the disks and to a ground if one is available.